Open the page you want to check. Anything your browser can open works: live sites, localhost, staging servers and pages behind a login.
Click the bookmark. This checker opens in a new tab with that page's tags.
The bookmarklet reads the page's HTML the way crawlers receive it and compares it with the page on screen, so it can spot tags that only JavaScript adds. Nothing is uploaded: the tags travel in the part of the link after #, which never leaves your browser.
Result
Crawlers
Each app sends its own bot to read a shared link. Most sites give them all the same page, but firewalls, bot protection and prerendering services can treat them differently, so every check asks all of them. The previews below show one version; use Show to switch.
Link previews
Close copies of each app's current layout.
Checks
Share image
Edit tagspreviews and checks update as you type
HTML for your <head>
All tags found
Tag
Value
Checking a page that isn’t public yet
While you build a site, its pages live at addresses like http://localhost:3000/blog/post or behind a staging login, and no online preview tool can open them. This page opens on the Bookmarklet tab for that case:
Drag the Check OG tags button to your browser’s bookmarks bar (show the bar with Ctrl+Shift+B, or ⌘+Shift+B on a Mac).
Open your local page in the same browser: the dev server, a preview deployment, an intranet page.
Click the bookmark. A new tab opens here with that page’s tags, the previews for Facebook, X, LinkedIn, WhatsApp, iMessage, Slack and Discord, and the full list of checks.
Keep the bookmark: one click checks any page you’re working on, after every change.
Two other ways in
Paste HTML: use View Source on the local page, copy everything, and paste it into the Paste HTML tab. Add the page’s future public address in the field below it, so relative image paths resolve the way they will on the live site.
Open .html file: a static site’s built output can be opened straight from disk.
Before you deploy
Local pages often carry tags that only break in production. The checks flag a relative image path and tags injected by client-side code; also read the og:image and og:url values in the All tags list, which on a dev server often still point at localhost. Once the site is live, switch to the Page URL tab of the Open Graph checker to see what each platform’s crawler really receives.